Furnace door



O. L. BRAUN FURNACE DOOR July 14, 1953 Filed May 25, 1951 I3 I8 22 I7 7 illsllu 3 INVENTOR.

QTTWIN L. BRAUN.

3 It; ATTORNEYS.

Patented July 14, 1953 lj-L-i I g FURNACE 1300a g g I Ottwin L. Braun, Pittsburgh,;P a;, assignor to Reliance Steel Products Company, McKeesport, Pa., a corporation of Pennsylvania.

Application May 25, 1951;:se'ria1No. 228,201"

This invention relates, as indicated, to a furnace door, and, more particularly, to an improved door of the hollow water-cooled type.

The practice of providing the inner or furnace side of hollow water-cooled doors with a protective refractory lining is well-known. Such protective linings are generally either of two different types. In one type, the inner surface of the door is lined with refractory bricks which are laid in position. The other type is known as the monolithic type, in which a protective lining of refractory material is applied to the inner surface of the door in a plastic condition. This invention is concerned with a furnace door having a protective refractory lining of the monolithic type.

Furnace doors having monolithic refractory linings are commonly provided with a plurality of studs projecting from the inner surface to which the refractory lining is applied. The studs have a dual purpose, in that they anchor the lining in position and transfer heat for the purpose of cooling the exposed surface of the lining. The studs may be formed of copper to increase their heat-conducting properties, and

thereby increase the life of the protective lining. However, in the course of time, the lining becomes worn and the ends of the studs are exposed. It is then necessary to-replace the lining, and this is a difiicult task, since the oldlining must be dug out of the space surrounding the projecting studs.

One of the principal objects of this invention is to provide an improved hollow furnace door which will eliminate the necessity of providing studs for cooling and anchoring a monolithic lining. To this end, the interior or furnace side of the door has a stepped construction thereby providing door surfaces at different levels, The door is constructed of sheet metal, and the sheets providin the surfaces at different levels are joined by inclined flanges providing in effect an undercut around the edges of the various steps. This undercut is effective to provide an anchor for holding the monolithic lining in place. The stepped construction of the interior surface of the door enables some of the metal sheets forming such interior surface to be positionedcloser to the exposed surface of the lining, and is thereby effective to maintain the lining at a lower temperature than would otherwise be the case if the lining had a uniform depth over the entire surface of the door.

In a manner which will become apparent, the door of this invention embodies other improved remiss; (chin-498) features and advantages. These additional features and advantages will be apparent from the following description.

In the drawings, there is shown a preferred embodiment of the invention. In this showing: Fig. l is a sectional view taken substantially along the line 1-1 of Fig. 2; I Fig. 2 is a front elevational view of a door constructed'in accordance with the principles of this 4 invention; and I Fig; 3 is a sectional View taken substantially along theline III-IlI of Fig. 2, and showing the door mounted in position with respect to a furnace, the furnace being shown fragmentarily in section. I.

Referring first to Fig. 3, numeral I designates a furnace having an opening Zin a'wallthereof, which is adapted to be opened and closed bya door 3. Th'door. 3, in accordance with conventional practice,:ismounted for vertical movement in a water-cooled framel toandfrom the position illustrated, in which-it. is ing the opening v2. 5

The door 3 is fabricatedfromsheet steel and has welded joints which arev fluid-tight. The door 3 is of rectangular shape and has a front plate 5 forming its front surface, edge plate 6 forming its side surfaces, anda backplate-structure l of stepped configuration'formingthe in- .terior surface or furnace side of the door. I The plates 5, 6 and l form a fluid-tight. enclosure through which cooling water may be circulated to prevent overheating of the door. For this purpose, .the door is provided with a water inlet 8 through which water is delivered to the vertical pipes 9 and exhausted from the bottom of such pipes. The water emerging from the bottom of the pipes 9 circulates upwardly through the enclosure and out of an outlet opening ID. The door is provided with wash-out openings II and lugs l2 by which it may be raised and lowered in its frame 4, these features being common in the art.

This invention is concerned primarily with the structure of the back plate 1 which forms the interior or furnace side of the door. As indicated, this side of the door is formed by a sheet metal structure of stepped configuration. It includes a sheet metal margin l3 extending entirely around the periphery of the door'at and connected with the interior edge of the side plates 6. The interior surface of the stepped construction l is formed by a sheet metal base ,plate I4 of rectangular shape positioned-con trally of the door and parallel to the marginal shown clos- 3 plate I3. An intermediate plate I is mounted in a position between and parallel to the plates l3 and I4. The plate I4 is joined to the inner edge of the intermediate plate l5 by a flange l6 which extends entirely around the periphery of the plate l4 and diverges angularly outwardly or exteriorly with respect to the furnace toward the outer or front plate 5 of the door. In a similar manner, the inner edge of the marginal plate [3 is connected with the outer edge of the intermediate plate I5 by a flange I! which extends completely around the outer edge of the intermediate plate IS. The flange I! also diverges angularly outwardly or exteriorly with respect to the furnace toward the exterior plate 5.

It will be noted that the interior plate M has an area greater than the area defined by the inner edge ill of the intermediate plate 15. In a similar manner, the area defined by the inner edge IQ of the marginal plate I3 is greater than that defined. by the outer edge of the intermediate plate: I5. The inner edges of the marginal plate l3 and the intermediate plate thus overlap the-outer edges: of the next adjacent plate in a direction toward the back plate 5.

There is .thus provided a door having a stepped construction on its back or interior surface with the. flanges l6 and I! defining the edges of the Stepsbeing undercut. The undercut construction provided by the flanges l6 and I! is such that they are effective to anchor a refractory lining applied to-the interior surface of the door in a plastic. condition. The undercut or angular inclination of the flanges l6 and I! is in a direction effective to prevent the lining 26 from moving away from the plates [4 and 15. This undercut structure is very effective for anchoring the monolithic refractory lining 20 in position against the interior surface of the door.

In addition to the anchoring of the refractory lining, the stepped construction of the back plate or interior surface of the door provides an improved cooling arrangement for such lining. The stepped construction enables the intermediate plate l5 to be positioned closer to the surface of the lining 20 than would be otherwise possible. The plate l5 being closer to the surface of the refractory lining 20, the peripheral edge of the lining is maintained at a lower temperature than would otherwise be possible. Lowering of the temperature of the edge portion of the refractory lining of course increases its ability to withstand the wearing effect of the hot gases moving over its exposed surface. The stepped construction of the door also compensates for the manner in which wear takes place on linings applied to the interior surface of a door. Such linings wear to a concave shape, the center portion of the lining wearing more than the edge portions thereof, due to the fact that the hot gases contacting the center of the lining have a higher velocity than those contacting or moving over the surface of the edge surfaces. The stepped. construction of the door thus provides a thicker depth of refractory lining at the point where the greatest wear is experienced.

In the stepped construction of the back plate 1, as shown in the drawing, it will be noted that the surface areas of the plates [4 and I5 are roughly equal. Each of the areas of these plates constitutes a significant percentage of the total surface area of .the door, and this condition must exist if the desided cooling effect is to be accomplished. Moreover, the depth of each of the flanges l6 and i1 is significant as compared to 4 the total depth of the door, and this condition must exist if the desired anchoring effect of their undercut construction is to be had.

To increase the cooling action on the refractory lining, the upper and lower flanges I! are joined by a pair of vertically-extending pipes 22 through which cooling water may circulate. The pipes 22 are embedded in the lining 20, and are thus effective to cool such lining. In a similar manner, the upper and lower flanges [6 are joined by a pair of vertically-extending pipes 23, through which cooling water may circulate. The pipes 23, as illustrated, are embedded in the refractory lining 20. In addition to cooling the refractory lining-20, the pipes 22 and 23 provide an anchor for the lining 20 which is forced in back of such pipes when applied to a door in a plastic condition. Although the door is illustrated as being provided with a pair only of each of the pipes 22 and 23, it will be understood that a greaternumber of. such pipes may be employed if desired;

In accordance with conventional practice, the door has: a plurality of tell-tale openings providedby pipes 25 which extendfrom the exterior plate 5,.to the interior plates [4 and [5. The interior-surface of the lining 20 may thus be viewed from the'outside, or exterior side of the door and the condition of the lining periodically inspected. An'opening 2B is provided in the lower portion of the-door" for examining the condition of the 7 interior of .the furnace without the necessity of moving the entire door to an open position.

Attention is particularly invited to the fact that the stepped construction of the interior surface of the door provides an improved cooling arrangement for the refractory lining 20. In addition to this improved cooling, the undercut provided by the flanges l6 and l! is effective to anchor the lining 20 in position against the interior surface of the door. The anchoring and cooling actions are both enhanced by the provision of the water-circulating pipes 22 and 23.. .Although the stepped construction of a door is shown. as having a single plate 15 intermediate .the marginal plate I3 and the interior plate 14; itwill be apparent that the door may be constructed with a greater number of steps by the use of more than a single intermediate plate. If desired, two or more intermediate plates in spaced parallel planes may be employed.

While I have illustrated and described one specific embodiment of my invention, it will be understood'that this is merely by way of illustration, and that various changes and modification may be made therein within the contemplation of my invention and under the scope of the following claims.

I claim:

1. A water-cooled furnace door having front, back, and edge plates of sheet metal forming a fluid-tight enclosure, the back plate being of stepped construction and comprising a marginal plate connected with said edge plate around the periphery of the door, a base plate parallel to and spaced'from both said marginal and front plates, an intermediate plate between and parallel to said base and marginal plates and having a central opening therein, the surface areas of said base and intermediate plates each constituting a significant percentage of the total surface area of.said backplate, a peripheral flange projecting interiorly from the outer peripheral edge ofysaidintermediate plate and connected with. said marginal plate,- a peripheral flange projecting exteriorly from the inner peripheral edge of said intermediate plate and connected with said base plate, and a monolithic filling of refractory material in the space centrally of said marginal plate.

2. A door as claimed in claim 1 wherein the depth of each of said flanges is a significant percentage of the total depth of the door.

3. A door as claimed in claim 1 wherein the inner peripheral edges of said marginal and intermediate plates overlap the outer edge of the plate immediately exteriorly thereof, and said flanges-diverge toward the front of the door thereby providing an under-cut construction for anchoring the said refractory material against movement away from said back plate.

4. A Water-cooled furnace door having front, 9

back, and edge plates of sheet metal forming a fluid-tight enclosure, the back plate being of stepped construction and comprising a marginal plate connected with said edge plate around the periphery of the door, a base plate parallel to and spaced from both said marginal and front plates, an intermediate plate between and parallel to said base and marginal plates and having a central opening therein, the surface areas of said base and intermediate plates each constituting a significant percentage of the total surface area of said back plate, a peripheral flange projecting interiorly from the outer peripheral edge of said intermediate plate and connected with said References Cited in-the file of this patent UNITED STATES PATENTS Number Name Date 1,369,338 Hillman -1- Feb. 22, 1921 1,509,932 Copeman Sept. 30, 1924 2,046,909 Terry et a1. July 7, 1936 2,169,060 Steinbacher Aug. 8, 1939 2,273,775 Strong Feb. 17, 1942 2,551,941

Greene May 3, 1951 

